Key takeaways
- Top pick: Redwood Materials, best for: Battery makers, carmakers and grid operators.
- Also near the top: Octopus Energy, best for: Households and businesses switching to renewable-backed tariffs; and Fervo Energy, best for: Utilities and data centres buying firm clean power.
- How it was ranked: 10 startups compared. Each verdict is below.
Best Climate Tech Startups: Top 10 Ranked. Redwood Materials ranks first, with a Lister Score of 96.9.
Redwood Materials leads climate tech startups globally in battery recycling and grid storage, and
Octopus Energy has the largest customer base, with more than 7 million energy customers.
Fervo Energy is the most proven next-generation geothermal developer, and
Form Energy leads long-duration iron-air battery storage.
Best Climate Tech Startups in 2026, compared| RANK | ENTRY | BEST FOR | SCORE | FROM |
|---|
| 1 |  Redwood MaterialsNVIDIA's venture arm, NVentures, joined Redwood's $350 million Series E, led by Eclipse. | Battery makers, carmakers and grid operators | 96.9 | Custom |
|---|
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| 2 |  Octopus EnergyOctopus says it serves more than 7.2 million customers, and Kraken has over 50 million contracted accounts. | Households and businesses switching to renewable-backed tariffs | 95.6 | Custom |
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| 3 |  Fervo EnergyFervo has 658 megawatts of contracted power purchase agreements and a 3-gigawatt geothermal framework agreement with Google. | Utilities and data centres buying firm clean power | 94.4 | Custom |
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| 4 |  Form EnergyForm signed a 12 GWh battery agreement with Crusoe Energy for AI data centres in March 2026. | Utilities planning multi-day backup for wind and solar | 93.1 | Custom |
|---|
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| 5 |  Antora EnergyAntora says it commissioned a 5 GWh thermal battery system in South Dakota in under 12 months. | Manufacturers replacing fossil-fuelled heat | 91.8 | Custom |
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| 6 |  WatershedWatershed's customers include General Mills, BBVA, Spotify and Klarna, and four of the top six US banks. | Sustainability teams seeking granular emissions measurement | 90.5 | – |
|---|
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| 7 |  Group14 TechnologiesGroup14's 10 GWh factory in Sangju, South Korea, began deliveries in September 2024. | Cell makers and device brands seeking faster charging and higher energy | 89.2 | Custom |
|---|
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| 8 |  TwelveTwelve secured a credit facility of up to $45 million for AirPlant One with Nomura and Endurance Capital. | Airlines and chemical buyers seeking low-carbon fuels | 87.9 | Custom |
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| 9 |  HeirloomHeirloom's carbon removal buyers include Microsoft, Meta, United Airlines and Shopify. | Buyers of direct air capture removal in the US | 86.6 | Custom |
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| 10 |  Rondo EnergyRondo says it has announced 11 commercial developments, including eight heat battery deployments, and has raised more than $160 million. | Industrial plants electrifying heat and steam | 85.3 | Custom |
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How to choose
Start from what you need it for. Where each entry fits best:
- Redwood Materials (#1): Battery makers, carmakers and grid operators
- Octopus Energy (#2): Households and businesses switching to renewable-backed tariffs
- Fervo Energy (#3): Utilities and data centres buying firm clean power
- Form Energy (#4): Utilities planning multi-day backup for wind and solar
- Antora Energy (#5): Manufacturers replacing fossil-fuelled heat
- Watershed (#6): Sustainability teams seeking granular emissions measurement
- Group14 Technologies (#7): Cell makers and device brands seeking faster charging and higher energy
- Twelve (#8): Airlines and chemical buyers seeking low-carbon fuels
- Heirloom (#9): Buyers of direct air capture removal in the US
- Rondo Energy (#10): Industrial plants electrifying heat and steam
Each entry's full verdict is below.
The ranking, in detail
01
Battery recycling and grid energy storage
Redwood Materials, founded in 2017 and based in Nevada, recycles end-of-life batteries to recover lithium, nickel, cobalt and copper, and has added a grid energy storage business. It raised a $350 million Series E led by Eclipse in October 2025.
PROS- Large-scale recycling operations
- Two linked revenue lines
CONS- Capital-heavy business
- Prices not published
- Best for
- Battery makers, carmakers and grid operators
- Where it falls short
- Prices are not published, so you cannot assess costs upfront.
- Pick something else if
- you need transparent pricing before committing.
96.9
02
Renewable energy supplier and Kraken software
Octopus Energy, founded in 2015 and based in London, supplies renewable-backed electricity to homes and businesses and runs Kraken, a software platform licensed to other energy companies.
PROS- Very large customer base
- Software licensed to other utilities
CONS- Tariffs vary by country
- Exposed to energy market swings
- Best for
- Households and businesses switching to renewable-backed tariffs
- Where it falls short
- Tariffs vary by country.
- Pick something else if
- you live in a country where it does not offer tariffs.
95.6
03
Enhanced geothermal power
Fervo Energy, founded in 2017 and based in Houston, develops enhanced geothermal power plants using drilling methods from oil and gas, led by Cape Station in Utah. It listed on Nasdaq in May 2026, raising about $2.2 billion.
PROS- Firm, always-on clean power
- Large contracted demand
CONS- First large plant just coming online
- Heavy capital spending
- Best for
- Utilities and data centres buying firm clean power
- Where it falls short
- It is not yet fully operational as its first large plant is just coming online.
- Pick something else if
- you need immediate power availability.
94.4
04
Iron-air batteries for multi-day storage
Form Energy, founded in 2017 and based in Somerville, Massachusetts, makes iron-air batteries that store electricity for up to 100 hours, built at its factory in Weirton, West Virginia. It raised a $750 million Series G in August 2026.
PROS- Stores energy for days, not hours
- Uses low-cost iron
CONS- First projects running behind schedule
- Early commercial stage
- Best for
- Utilities planning multi-day backup for wind and solar
- Where it falls short
- First projects are running behind schedule.
- Pick something else if
- you need immediate commercial operation.
93.1
05
Thermal batteries for industrial heat and power
Antora Energy, founded in 2018 and based in San Jose, California, builds thermal batteries that store clean electricity as heat for factories and industrial sites. It raised a $550 million Series C in July 2026.
PROS- Large commissioned project
- Own manufacturing in California
CONS- Few large sites so far
- Prices not published
- Best for
- Manufacturers replacing fossil-fuelled heat
- Where it falls short
- Few large sites so far.
91.8
06
Industry-leading sustainability AI for smarter business decisions
Watershed, founded in 2019 in San Francisco, sells software that helps companies measure, report and cut their emissions. It raised a $100 million Series C at a $1.8 billion valuation in February 2024.
PROS- The product delivers granular measurements using built-in data and methodologies.
- Watershed accelerates reporting through AI drafting and peer benchmarks.
- Best for
- Sustainability teams seeking granular emissions measurement
90.5
07
Silicon-carbon anode material for lithium-ion batteries
Group14 Technologies, founded in 2015 and based in Woodinville, Washington, makes silicon-carbon anode material for lithium-ion batteries. It closed a $463 million Series D led by SK in August 2025 and took full ownership of its factory in Sangju, South Korea.
PROS- Drop-in material for existing cell factories
- Large customer base
CONS- Supplies materials, not finished batteries
- Competes with other silicon anode makers
- Best for
- Cell makers and device brands seeking faster charging and higher energy
- Where it falls short
- It supplies raw materials rather than finished batteries.
- Pick something else if
- you need complete battery packs.
89.2
08
Fuels and chemicals made from captured CO2
Twelve, founded in 2015, converts carbon dioxide, water and renewable electricity into fuels and chemicals. Its first plant, AirPlant One in Moses Lake, Washington, is now operating.
PROS- Operating commercial plant
- Makes drop-in aviation fuel
CONS- Small output so far
- Prices not published
- Best for
- Airlines and chemical buyers seeking low-carbon fuels
- Where it falls short
- It has small output so far and prices are not published.
- Pick something else if
- you need large volume or known pricing.
87.9
09
Limestone-based direct air capture
Heirloom, founded in 2020 in San Francisco, captures carbon dioxide from the air using limestone and stores it permanently. It runs what it calls America's first commercial direct air capture facility, in California's Central Valley, and is developing two plants in Louisiana.
PROS- Uses cheap, abundant limestone
- Commercial plant already running
CONS- Louisiana plants not yet operating
- Small capture volumes so far
- Best for
- Buyers of direct air capture removal in the US
- Where it falls short
- It currently offers small capture volumes and its Louisiana plants are not yet operating.
- Pick something else if
- you need large scale capacity right now.
86.6
10
Heat batteries for industry
Rondo Energy, founded in 2020 and based in Alameda, California, makes heat batteries that store renewable electricity and release it as high-temperature industrial heat and steam.
PROS- Replaces gas-fired boilers
- Project in development with Rio Tinto
CONS- Few operating sites disclosed
- Prices not published
- Best for
- Industrial plants electrifying heat and steam
- Where it falls short
- Prices are not published, so you cannot assess costs upfront.
- Pick something else if
- you need transparent pricing before committing.
85.3
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Frequently asked questions
What are the best Climate Tech Startups?
Redwood Materials ranks first on Lister. Redwood Materials, founded in 2017 and based in Nevada, recycles end-of-life batteries to recover lithium, nickel, cobalt and copper, and has added a grid energy storage business. It raised a $350 million Series E led by Eclipse in October 2025.
What are the top 10 Climate Tech Startups?
1. Redwood Materials; 2. Octopus Energy; 3. Fervo Energy; 4. Form Energy; 5. Antora Energy; 6. Watershed; 7. Group14 Technologies; 8. Twelve; 9. Heirloom; 10. Rondo Energy.
Sources
Where we checked each company's facts, and when.
Some links on Lister are affiliate links. Rankings are not affected.
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